<template>
  <div class="music-list" ref="music_list">
    <div class="back" @click="back">
      <i class="icon-back"></i>
    </div>
    <h1 class="title" v-html="title"></h1>
    <div class="bg-image" :style="bgStyle" ref="bgImage">
      <div class="play-wrapper">
        <div ref="playBtn" v-show="songs.length>0" class="play" @click="randomAll">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" ref="filter"></div>
    </div>
    <!-- bg-layer在文档流中，处在 bg-image下面 -->
    <div class="bg-layer" ref="layer"></div>
    <scroll @scroll="scroll" :needEmitScroll="needEmitScroll" :probeType="probeType" :data="songs" class="list" ref="list">
      <div class="song-list-wrapper">
        <song-list @selectItem="selectSong" :data="songs" :rank="rank"></song-list>
      </div>
      <div v-show="!songs.length" class="loading-container">
        <loading></loading>
      </div>
    </scroll>
  </div>
</template>

<script type="text/ecmascript-6">
import Scroll from 'base/scroll/scroll'
import SongList from 'base/song-list/song-list'
import { prefixStyle } from 'common/js/dom'
import Loading from 'base/loading/loading'
import { mapActions, mapGetters } from 'vuex'
import { playlistMixin } from 'common/js/mixin'

const RESERVED_HEIGHT = 40
const transform = prefixStyle('transform')
const backdrop = prefixStyle('backdrop-filter')

export default {
  mixins: [
    playlistMixin
  ],
  components: {
    SongList,
    Scroll,
    Loading
  },
  data() {
    return {
      imageHeight: 0,
      scrollY: 0
    }
  },
  props: {
    title: {
      type: String,
      default: 'Default Title'
    },
    songs: {
      type: Array,
      default: () => { return [] }
    },
    avatar: {
      type: String,
      default: ''
    },
    rank: {
      type: Boolean,
      default: false
    }
  },
  methods: {
    handlePlaylist(newList) {
      // console.log('set music_list bottom')
      if (newList.length > 0) {
        this.$refs.list.$el.style.bottom = '60px'
        this.$refs.list.refresh()
      } else {
        this.$refs.list.$el.style.bottom = '0px'
        this.$refs.list.refresh()
      }
    },
    randomAll() {
      // 随机播放全部歌曲
      let currentSongId = this.currentSong().id
      this.randomPlay({
        list: this.songs,
        songid: currentSongId
      })
    },
    back() {
      this.$router.back()
    },
    scroll(pos) {
      this.scrollY = pos.y
    },
    selectSong(list, index) {
      this.selectPlay({
        list: this.songs,
        index: index
      })
    },
    ...mapGetters({
      currentSong: 'currentSong'
    }),
    ...mapActions({
      selectPlay: 'selectPlay',
      randomPlay: 'randomPlay'
    })
  },
  computed: {
    bgStyle() {
      return `background-image:url(${this.avatar})`
    }
  },
  watch: {
    scrollY(newY) {
      let needTransform = newY
      needTransform = Math.max(this.minTransalteY, needTransform)

      let scale = 1
      let zIndex = 0
      let blur = 0
      const percent = Math.abs(newY / this.imageHeight)
      if (newY > 0) {
        scale = 1 + percent
      } else {
        blur = Math.min(20, percent * 20)
      }
      // this.$refs.layer.style['transform'] = `translate3d(0, ${needTransform}px, 0)`
      this.$refs.layer.style[transform] = `translate3d(0, ${needTransform}px, 0)`
      this.$refs.filter.style[backdrop] = `blur(${blur}px)`
      if (newY <= this.minTransalteY) {
        zIndex = 10
        this.$refs.bgImage.style['padding-bottom'] = 0
        this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
        this.$refs.playBtn.style.display = 'none'
      } else if (newY > 0) {
        zIndex = 10 // scale>1的情况下，背景图片放大，需要覆盖 .list的视窗
      } else {
        zIndex = 0
        this.$refs.bgImage.style.height = 0
        this.$refs.bgImage.style.paddingBottom = '70%'
        this.$refs.playBtn.style.display = ''
      }

      this.$refs.bgImage.style[transform] = `scale(${scale})`
      this.$refs.bgImage.style.zIndex = zIndex
    }
  },
  created() {
    this.needEmitScroll = true
    this.probeType = 3
  },
  mounted() {
    this.imageHeight = this.$refs.bgImage.clientHeight
    this.minTransalteY = -this.imageHeight + RESERVED_HEIGHT
    // 因为图片高度不确定，所以scroll的top也不确定，需要在mounted后才能确定scroll的top
    this.$refs.list.$el.style.top = `${this.imageHeight}px`
  }
}
</script>
<style scoped lang="stylus" rel="stylesheet/stylus">
@import "~common/stylus/variable"
@import "~common/stylus/mixin"

.music-list
  position: fixed
  z-index: 100
  top: 0
  left: 0
  bottom: 0
  right: 0
  background: $color-background
  .back
    position absolute
    top: 0
    left: 6px
    z-index: 50
    .icon-back
      display: block
      padding: 10px
      font-size: $font-size-large-x
      color: $color-theme
  .title
    position: absolute
    left: 10%
    top: 0
    z-index: 40
    width: 80%
    no-wrap()
    text-align: center
    color: $color-text
    line-height: 40px
    font-size: $font-size-large
  .bg-image
    position: relative
    width: 100%
    height: 0
    padding-bottom: 70%
    background-size: cover
    .play-wrapper
      position: absolute
      bottom: 20px
      z-index: 50
      width: 100%
      .play
        box-sizing: border-box
        width: 135px
        padding: 7px 0
        margin: 0 auto
        text-align: center
        border: 1px solid $color-theme
        color: $color-theme
        border-radius: 15px
        font-size: 0
        .icon-play
          display: inline-block
          vertical-align: middle
          margin-right: 6px
          font-size: $font-size-medium-x
        .text
          display: inline-block
          vertical-align: middle
          font-size: $font-size-small
    .filter // 背景图片模糊层
      position: absolute
      top: 0
      left: 0
      width: 100%
      height: 100%
      background: rgba(7, 17, 27, 0.4)
  .list
    position: fixed
    top: 0
    bottom: 0
    width: 100%
    background: $color-background
    overflow: visible
    .song-list-wrapper
      padding: 20px 30px
    .loading-container
      position: absolute
      width: 100%
      top: 50%
      transform: translateY(-50%)
  .bg-layer
    width: 100%
    background: $color-background
    height: 100%
</style>
